Complete spectral assignments and microstructures of photopolymerized acrylonitrile methacrylic acid copolymers by NMR spectroscopy

Copolymers of acrylonitrile/methacrylic acid were prepared by photopolymerization using the uranyl ion as a photosensitizer. The comonomer reactivity ratios, determined by both Kelen-Tudos (KT) and nonlinear error in variables (EVM) methods are r(A) = 0.135 +/- 0.04 and r(M) = 3.618 +/- 0.49. The microstructure was obtained in terms of the distribution of A- and M-centered triad sequences from C-13-{H-1} NMR spectra of the copolymers. Homonuclear 2D TOCSY NMR was used to simplify the complex H-1 spectra of A/M copolymers in terms of configurational/conformational sequences. The triad concentration calculated from Monte Carlo simulations (MC) gave good agreement with the triad concentration determined from NMR spectroscopy. MC simulation was also used to study the effect of the degree of polymerization on triad fractions.